It has long been a desire of pitchers, coaches, trainers and others involved in baseball and softball to have a relatively inexpensive, easy to use and accurate device that could not only measure the speed of a pitched ball, but also whether it was in the strike zone. Radar guns, if properly used, can measure the velocity of a pitched ball, but cannot tell if the pitch was a ball or strike.
A number of devices have been proposed for measuring both the velocity and position of objects in flight. For example, U.S. Pat. No. 4,563,005 issued Jan. 7, 1985 to Richard A. Hand describes a device for computing the speed and location of a baseball as it is pitched over a plate. This device uses two vertical arrays of infrared transmitters to establish two parallel planes through which the ball must pass. The speed of the ball is determined by measuring the time it takes for the ball to pass through the zone between the parallel planes, and the coordinate position of the ball is calculated by computer circuitry based on a preprogrammed table of angular data. This device requires 128 emitters, 8 receivers, and a central processing unit with access to a program stored in a read only memory device. Thus, this unit is inherently expensive, and has three major components that must be interconnected prior to operation. Further, the device requires considerable electrical energy to drive the large number of emitters and the computer. These disadvantages render the device undesirable portable operation, especially at a location which is dependent on a battery source for electrical power.
Another device for evaluating ball pitching performance, described in U.S. Pat. No. 5,230,505 issued Jul. 27, 1993 to Ghislain Paquet et al, uses two arrays of infrared emitters and two arrays of corresponding infrared receivers to form a three dimensional system bounded by two planes. The device is housed in a framework that forms a corridor with a display unit disposed near a forward end of the corridor and the three dimensional measuring zone disposed adjacent the rearward end. Thus this device similarly requires a significant amount of electrical energy to operate, and its unwieldy size makes it similarly unsuitable for portable operation at sites remote from a source of electrical energy
A device for measuring the velocity and position of an object in flight is described in U.S. Pat. No. 4,770,527, issued Sep. 13, 1988 to Kyung T. Park. The Park device uses two arrays of transmitters and receivers, aligned at right angles in a single plane, and an impact sensor formed of a sheet of piezoelectric polymer material having layers of electroconductive material on the front and back. The velocity of the object is calculated by measuring the time lapse between interruption of the plane and contact with the impact sensor. The position of impact is determined by dividing the impact sensor into a plurality of zones and then sensing the zone struck by the object. It is believed that an impact sensor as proposed by Park would inherently have a short life when repeatedly struck by a baseball traveling at a speed of 80 to 90 mph.
A device for measuring the velocity of an object in motion, and the change of velocity of the object as it passes through a zone bounded by parallel planes is described in U.S. Pat. No. 4,180,726 issued Dec. 25, 1979 to Ronald DeCrescent. In addition to requiring two detection planes, the DeCrescent device cannot determine the lateral position of the moving object as it passes through the zone. Thus, this device would be unsuitable for determining the zonal position of a baseball.
The present invention is directed to overcoming the problems set forth above. It is desirable to have a method for simultaneously determining the velocity and zonal position of a baseball as it passes through a single vertical plane. It is also desirable to have a rugged, relatively inexpensive device for carrying out that method comprising only a single linear array of transmitters and receivers and which can be powered for an extended period of time by electrical energy stored in a conventional battery. Furthermore, it is desirable to have such a device in which all of the components are advantageously assembled together in a single unit that is easily transportable to a desired site, either indoors or outdoors.